Core rule: section 18(4), inserted by Finance Act 2083, allows a taxpayer to amend a return filed within the statutory deadline within seven days of submitting it, following the Department's prescribed process. The seven days run from filing, not from discovering the error.
Reconcile the invoice records, prepare the corrected figures and use the authorised correction process. Keep both versions and the submission acknowledgement. A correction is not a waiver of tax, interest or applicable fees.
Example: an omitted taxable sale is NPR 50,000 excluding VAT. At 13%, the missing output VAT is NPR 6,500. Correct the affected return through the authorised process and pay the resulting amount due.
After seven days, or for a late-filed return, contact the tax office for the applicable route. Do not silently offset an old omission in an unrelated later return.